| Subject: | Suggested policy: prohibit conditional use statements |
When maintaining legacy code I occasionally see constructs similar to
the following:
if (some_condition()) {
use Module;
Module::do_something();
} else {
use SomeOtherModule;
SomeOtherModule::do_something_else();
}
The original author probably meant to conditionally load modules, but
was unaware the "use" statements were evaluated at compile-time.
I created a policy tentatively titled
Modules::ProhibitConditionalUseStatements to catch this type of assumption.
Presently it will catch the following:
# if-elsif-else
if ($a == 1) { use Module; }
if ($a == 1) { } elsif ($a == 2) { use Module; }
if ($a == 1) { } else { use Module; }
# for/foreach
for (1..$a) { use Module; }
foreach (@a) { use Module; }
# while
while ($a == 1) { use Module; }
# unless
unless ($a == 1) { use Module; }
# until
until ($a == 1) { use Module; }
# do-condition
do { use Module; } if $a == 1;
do { use Module; } while $a == 1;
do { use Module; } unless $a == 1;
do { use Module; } until $a == 1;
# operator-do
$a == 1 || do { use Module; };
$a == 1 && do { use Module; };
$a == 1 or do { use Module; };
$a == 1 and do { use Module; };
# non-string eval
eval { use Module; };
but will allow:
# bare block
{ use Module; }
# do
do { use Module; }
# string eval
eval "use Module";
I welcome any feedback you might have regarding the naming or even how
useful (no pun intended) you consider this policy to be.
Thanks
| Subject: | ProhibitConditionalUseStatements.pm |
##############################################################################
# $URL$
# $Date$
# $Author$
# $Revision$
##############################################################################
package Perl::Critic::Policy::Modules::ProhibitConditionalUseStatements;
use 5.006001;
use strict;
use warnings;
use Readonly;
use Perl::Critic::Utils qw{ :booleans :severities };
use base 'Perl::Critic::Policy';
our $VERSION = '1.108';
#-----------------------------------------------------------------------------
Readonly::Scalar my $DESC => q{Conditional "use" statement};
Readonly::Scalar my $EXPL => q{Use "require" to conditionally include a module.};
# operators
Readonly::Hash my %OPS => map { $_ => 1 } qw( || && or and );
#-----------------------------------------------------------------------------
sub supported_parameters { return () }
sub default_severity { return $SEVERITY_MEDIUM }
sub default_themes { return qw( core bugs ) }
sub applies_to { return 'PPI::Statement::Include' }
#-----------------------------------------------------------------------------
sub violates {
my ( $self, $elem, $doc ) = @_;
return $self->violation( $DESC, $EXPL, $elem ) if $elem->type() eq 'use'
&& !$elem->pragma()
&& $elem->module()
&& $self->_is_in_conditional_logic($elem);
return;
}
#-----------------------------------------------------------------------------
# is this a non-string eval statement
sub _is_eval {
my ( $self, $elem ) = @_;
$elem->isa('PPI::Statement') or return;
my $first_elem = $elem->first_element();
return $TRUE if $first_elem->isa('PPI::Token::Word')
&& $first_elem eq 'eval';
return;
}
#-----------------------------------------------------------------------------
# is this in a conditional do block
sub _is_in_do_conditional_block {
my ( $self, $elem ) = @_;
return if !$elem->isa('PPI::Structure::Block');
my $prev_sibling = $elem->sprevious_sibling() or return;
if ($prev_sibling->isa('PPI::Token::Word') && $prev_sibling eq 'do') {
my $next_sibling = $elem->snext_sibling();
return $TRUE if $next_sibling
&& $next_sibling->isa('PPI::Token::Word');
$prev_sibling = $prev_sibling->sprevious_sibling() or return;
return $TRUE if $prev_sibling->isa('PPI::Token::Operator')
&& $OPS{$prev_sibling->content()};
}
return;
}
#-----------------------------------------------------------------------------
# is this a compound statement
sub _is_compound_statement {
my ( $self, $elem ) = @_;
return if !$elem->isa('PPI::Statement::Compound');
return $TRUE if $elem->type() ne 'continue'; # exclude bare blocks
return;
}
#-----------------------------------------------------------------------------
# is this contained in conditional logic
sub _is_in_conditional_logic {
my ( $self, $elem ) = @_;
while ($elem = $elem->parent()) {
last if $elem->isa('PPI::Document');
return $TRUE if $self->_is_compound_statement($elem)
|| $self->_is_eval($elem)
|| $self->_is_in_do_conditional_block($elem);
}
return;
}
1;
__END__
#-----------------------------------------------------------------------------
=pod
=head1 NAME
Perl::Critic::Policy::Modules::ProhibitConditionalUseStatements - Avoid putting conditional logic around compile-time includes.
=head1 AFFILIATION
This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.
=head1 DESCRIPTION
Modules included via "use" are loaded at compile-time. Placing conditional
logic around the "use" statement has no effect on whether the module will be
loaded. Doing so can also serve to confuse the reader as to the author's
original intent.
If you need to conditionally load a module you should be using "require"
instead.
This policy will catch the following forms of conditional "use" statements:
# if-elsif-else
if ($a == 1) { use Module; }
if ($a == 1) { } elsif ($a == 2) { use Module; }
if ($a == 1) { } else { use Module; }
# for/foreach
for (1..$a) { use Module; }
foreach (@a) { use Module; }
# while
while ($a == 1) { use Module; }
# unless
unless ($a == 1) { use Module; }
# until
until ($a == 1) { use Module; }
# do-condition
do { use Module; } if $a == 1;
do { use Module; } while $a == 1;
do { use Module; } unless $a == 1;
do { use Module; } until $a == 1;
# operator-do
$a == 1 || do { use Module; };
$a == 1 && do { use Module; };
$a == 1 or do { use Module; };
$a == 1 and do { use Module; };
# non-string eval
eval { use Module; };
Including a module via "use" in bare blocks, standalone do blocks, or
string evals is allowed.
# bare block
{ use Module; }
# do
do { use Module; }
# string eval
eval "use Module";
=head1 CONFIGURATION
This Policy is not configurable except for the standard options.
=head1 AUTHOR
Peter Guzis <pguzis@cpan.org>
=head1 COPYRIGHT
Copyright (c) 2010 Peter Guzis. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself. The full text of this license
can be found in the LICENSE file included with this module.
=cut
# Local Variables:
# mode: cperl
# cperl-indent-level: 4
# fill-column: 78
# indent-tabs-mode: nil
# c-indentation-style: bsd
# End:
# ex: set ts=8 sts=4 sw=4 tw=78 ft=perl expandtab shiftround :
| Subject: | ProhibitConditionalUseStatements.run |
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